III-V crystals are of interest in a number of optical and electronic applications because these crystals can have a wide band gap. E.g., in certain opto-electronic devices, III-V crystals can be used to emit light at wavelengths (e.g. blue light) that would otherwise be difficult to attain. It can be difficult, however, to grow epitaxial layers of III-V crystals, or to grow such crystals to a suitable size for practical application. It can also be difficult to grow epitaxial layers of III-V crystals on particular types of crystalline substrates, e.g., silicon, because the lattice constant of the III-V crystals does not match the lattice constants of the substrates. In particular, growing a group III-V crystal on a substrate with different lattice constants typically caused defects to be formed in the group III-V crystal. If a grown III-V crystal has an excessive number of defects, then the opto-electronic properties of the crystal will suffer (e.g., decreased light emitting efficiency, or substantially increased or decreased electrical resistivity).